Effect of Different Salt on Fabrication of Sr0.5Ba0.5Nb2O6 by Molten-Salt Synthesis

Abstract:

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In the present work, effects of different salts (NaCl, 0.5NaCl-0.5KCl and KCl) on
molten-salt-synthesized Sr0.5Ba0.5Nb2O6 (SBN50) powder were explored. A variety of particle
morphology, compositions and lattice parameters of SBN50 were investigated. The results
showed that SBN50 particles synthesized in NaCl salt have the finest diameter (0.1-0.2μm) and the
highest aspect ratio (around 10), while the particles from 0.5NaCl-0.5KCl salt show the coarsest
diameter (0.2-0.3μm) and the lowest aspect ratio (around 5). If only using KCl salt, trace Sr2Nb2O7
normally co-exists with SBN50 phase. In addition, Na+ and K+ cations from salts are easily
incorporated with SBN structure and reach a very high content.

Abstract: Synthesis of nano TiC powder by carbothermal reduction procedure of TiO2 was
investigated. TiO2 was mixed with resin or carbon powder as reduction agent and was reacted at
1500oC for 0 ~ 45 minutes under Ar atmosphere. Conglomeration of the powders mixed with TiO2
and resin were observed in the initial stage of the reduction and the unreacted TiO2 was not found
even after 5 minutes elapsed. The fine TiC particles with a size of 80 nm were formed by complete
reaction between Ti, a reduction product, and C after 15 minutes. However, the conglomerated
particles were not the powders added with carbon powder as carbon source in the initial stage. The
unreacted TiO2 particles were kept for 15 minutes. Finally, TiC particles were formed and were
partially grown after 20 minutes.

Abstract: The magnetic anisotropy of Co/Ti-doped Ba ferrite particles for application in recording
media is studied. A method which deduces the anisotropy from the measurement of the reduced
perpendicular magnetization and allows to find also the distribution of anisotropy fields is
employed. The effect of the doping ions content, of the alignment degree of the particles and of the
variation of the temperature on the anisotropy is analysed and discussed, taking account of the
contemporary presence of magnetocrystalline and shape anisotropy, with different easy
magnetization axes, in the Ba ferrite particles.

Abstract: Alumina-iron nanocomposite powders containing 5vol.% of iron were fabricated by
high-energy ball milling with different ball-to-powder weight ratios (BPRs) as part of the study of
ceramic-metal nanocomposite magnetic materials. The microstructure and morphology of the
composite powders were characterized using the X-ray diffraction, optical microscopy and scanning
electron microscopy. XRD analysis and SEM examination in combination with energy dispersive
X-ray spectrometry confirmed that the nanocomposite structure of the powder particles formed only
after 8 hours milling for both BPRs used. With a higher BPR of 16:1, Fe-Cr alloy material was
broken from the stainless steel balls and incorporated into the nanocomposite powder. However,
such a problem did not occur with a lower BPR of 5:1. The mechanism for formation of the alumina
matrix nanocomposite powder is found to be dependent on BPR and milling time.

Abstract: Spherical submicrometer-sized silica particles were prepared from a reaction mixture containing tetraethoxysilane, ammonia and ethanol, and deposited onto silicon wafers. The properties of these SiO2 particles depend on their size, size distribution and shape. Even if some of these characteristics can be perfectly controlled by appropriate synthesis conditions, several alternative approaches must be explored in order to modify the shape of silica particles. The samples were then irradiated at room temperature with Si ions at different energies (4, 6 and 8 MeV) and fluences up to 5×1015 Si/cm2, at an angle of 45° with respect to the sample surface. After the Si irradiation the spherical silica particles turned into ellipsoidal particles, as a result of the increase of the particle dimension perpendicular to the ion beam and a decrease in the parallel direction. This effect increases with the ion fluence and depends on the electronic energy loss of the impinging ions. We observed that the particle deformation decreases with the beam energy, mainly because our samples were irradiated at room temperature. Thermal effects must be studied in detail in order to elucidate the complete deformation mechanism, as the existence of additional mechanisms related to the electronic energy loss effects can not be excluded.

Abstract: One-dimensional magnetite particles were prepared by a seed-mediated growth method under magnetic field. The amount of seed, seed size, PolyvinylPyrrolidone concentration (PVP) and reaction time have a significant effect on the morphology of the samples. The addition of a small amount of 100nm seeds leads to obtain rod-like particles, while chain-like particles are formed when the seed size is increased to 700 nm. The aspect ratio of the rod is controlled by varying the volume ratio of seed to iron salt. Increasing the reaction time is favorable to the formation of chain-like particles.